US8260209B2ActiveUtilityPatentIndex 60
System and method for coordinated spatial multiplexing using second order statistical information
Est. expiryNov 18, 2029(~3.4 yrs left)· nominal 20-yr term from priority
Inventors:SANAYEI SHAHAB
H01Q 1/246H04B 7/0634H04B 7/0617
60
PatentIndex Score
3
Cited by
14
References
14
Claims
Abstract
A system and method for coordinated spatial multiplexing using second order statistical information is provided. A method for controller operations includes receiving second order statistics from a plurality of communications devices, computing a beamforming vector for each communications device in the plurality of communications devices, selecting a subset of communications devices from the plurality of communications devices to receive transmissions, and transmitting transmissions to the subset of selected communications devices. The beamforming vector for a communications device is based on the second order statistics provided by the communications device, and the transmitting uses the computed beamforming vector for each selected communications device to transmit the transmissions to the selected communications device.
Claims
exact text as granted — not AI-modified1. A method for controller operations, the method comprising:
receiving second order statistics from a plurality of communications devices;
computing a beamforming vector for each communications device in the plurality of communications devices, wherein the beamforming vector for a communications device is based on the second order statistics provided by the communications device;
selecting a subset of communications devices from the plurality of communications devices to receive transmissions; and
transmitting transmissions to the selected subset of communications devices, wherein the transmitting uses the computed beamforming vector for each selected communications device to transmit the transmissions to the selected communications device,
wherein the plurality of communications devices comprises two communications devices,
wherein computing a beamforming vector comprises maximizing a sum-rate capacity for each of the two communications devices, and
wherein the sum-rate capacity for the two communications devices is expressible as:
C =log 2 (1 +SNR 1 )+log 2 (1 +SNR 2 )
where SNR i is a signal-to-noise ratio for an i-th communications device.
2. The method of claim 1 , wherein receiving second order statistics comprises receiving a spatial covariance matrix.
3. The method of claim 1 , wherein the two communications devices are operating in a high SNR environment, and wherein maximizing the sum-rate capacity comprises maximizing a cost function expressible as:
w
1
H
R
1
H
w
1
w
2
H
R
1
H
w
2
·
w
2
H
R
2
w
2
w
1
H
R
2
w
1
=
(
w
1
H
R
1
w
1
w
1
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R
2
w
1
)
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w
2
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R
2
w
2
w
2
H
R
1
w
2
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,
where R i is second order statistics from the i-th communications device, w i is the beamforming vector for the i-th communications device, w i H is a Hermitian of w i , R i H is the Hermitian of R i and i is 1 or 2.
4. The method of claim 3 , wherein w 1 is an eigen vector corresponding to a maximum eigen value of matrix R 2 −1 R 1 , expressible as
R 2 −1 R 1 ·w 1 =λ max ·w 1 ,
and wherein w 2 is an eigen vector corresponding to a minimum eigen value of matrix R 2 −1 R 1 , expressible as
R 2 −1 R 1 ·w 2 =λ min ·w 2 ,
where is the maximum eigen value, λ min is the minimum eigen value, and R i −1 is an inverse of R i .
5. The method of claim 1 , wherein two controllers communicate with the two communications devices using multi-terminal coordinated spatial multiplexing, wherein w ij are beamforming weights used by a j-th controller to transmit to an i-th communications device, and wherein w i1 is given by eigen vectors of R 12 −1 R 11 corresponding to maximum and minimum eigen values and w i2 is given by eigen vectors of R 21 −1 R 22 corresponding to maximum and minimum eigen values, where R ij is the second order statistics for a i-th communications device from an j-th controller, and R ij −1 is the inverse of R ij .
6. A method for communications device operations, the method comprising:
estimating a communications channel between the communications device and a controller;
estimating second order statistics for the communications channel based on the estimated communications channel;
transmitting the second order statistics to the controller, wherein the second order statistics are used by the controller to compute a beamforming vector to be used in communications to the communications device; and
receiving a transmission that uses the computed beamforming vector,
wherein the communications device is communicating with two controllers using multi-terminal coordinated spatial multiplexing, and wherein estimating the second order statistics comprises, evaluating
R 11 =E[h 11 h 21 H ] and R 21 =E[h 21 h 21 H ],
where R ij is the second order statistics for a i-th communications device from an j-th controller, h ij is a communications channel between the j-th controller and the i-th communications device, h ij H is the Hermitian of h ij , and E[.] is an expected value function.
7. The method of claim 6 , further comprising, prior to transmitting the second order statistics, smoothing the second order statistics.
8. The method of claim 7 , wherein smoothing the second order statistics comprises filtering the second order statistics.
9. The method of claim 8 , wherein filtering the second order statistics comprises applying an exponential averaging filter.
10. The method of claim 7 , further comprising, prior to transmitting the second order statistics, quantizing the second order statistics.
11. The method of claim 6 , wherein estimating a communications channel comprises sampling the communications channel at different times and frequencies, thereby producing time-frequency samples.
12. The method of claim 11 , wherein sampling the communications channel comprises sampling a pilot sequence or a reference sequence transmitted by the controller over the communications channel.
13. The method of claim 12 , wherein sampling the communications channel comprises sampling transmissions made over the communications channel for a period of time.
14. A method for communications device operations, the method comprising:
estimating a communications channel between the communications device and a controller;
estimating second order statistics for the communications channel based on the estimated communications channel, wherein the second order statistics comprise a spatial covariance matrix;
transmitting the second order statistics to the controller, wherein the second order statistics are used by the controller to compute a beamforming vector to be used in communications to the communications device; and
receiving a transmission that uses the computed beamforming vector, wherein estimating the second order statistics comprises evaluating
R
k
=
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,
where R k is the second order statistics for a k-th communications device, E[.] is an expected value function, h k is a communications channel for the k-th communications device, h k H is a Hermitian of h k , T is a set of time indices, F is a set of frequency indices of samples of the communications channel, h k (t,f) is a time-frequency sample of h k at time t and frequency f, and h k H (t,f) is a time-frequency sample of the Hermitian of h k at time t and frequency f.Cited by (0)
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